Image Resources
Optimizing Step 1: Scale down your image
Scale down your image to the size you intend for your website (No need for larger than 1920px wide in general)
External web link - http://www.simpleimageresizer.com/
Optimizing Step 2: Compress your image
Use tinypng.com to reduce your image file size for use on the web
External web link - https://tinypng.com/
Photodune
Affordable Stock Photos
External web link - https://photodune.net/
Unsplash
Another stock photo site
External web link - https://unsplash.com/